class-front-end.php

<?php

namespace Code_Snippets;

use WP_Post;
use WP_REST_Response;
use WP_REST_Server;

/**
 * This class manages the shortcodes included with the plugin,
 *
 * @package Code_Snippets
 */
class Front_End {

	/**
	 * Name of the shortcode tag for rendering the code source
	 */
	const SOURCE_SHORTCODE = 'code_snippet_source';

	/**
	 * Name of the shortcode tag for rendering content snippets
	 */
	const CONTENT_SHORTCODE = 'code_snippet';

	/**
	 * Handle to use for front-end scripts and styles.
	 */
	const PRISM_HANDLE = 'code-snippets-prism';

	/**
	 * Maximum depth for shortcode recursion.
	 */
	const MAX_SHORTCODE_DEPTH = 5;

	/**
	 * Class constructor
	 */
	public function __construct() {
		add_action( 'the_posts', [ $this, 'enqueue_highlighting' ] );
		add_action( 'init', [ $this, 'setup_mce_plugin' ] );

		add_shortcode( self::CONTENT_SHORTCODE, [ $this, 'render_content_shortcode' ] );
		add_shortcode( self::SOURCE_SHORTCODE, [ $this, 'render_source_shortcode' ] );

		add_filter( 'code_snippets/render_content_shortcode', 'trim' );
	}

	/**
	 * Register REST API routes for use in front-end plugins.
	 *
	 * @return void
	 */
	public function register_rest_routes() {
		register_rest_route(
			'v1/snippets',
			'/snippets-info',
			array(
				'methods'             => WP_REST_Server::READABLE,
				'callback'            => [ $this, 'get_snippets_info' ],
				'permission_callback' => function () {
					return current_user_can( 'edit_posts' );
				},
			)
		);
	}

	/**
	 * Fetch snippets data in response to a request.
	 *
	 * @return WP_REST_Response
	 */
	public function get_snippets_info(): WP_REST_Response {
		$snippets = get_snippets();
		$data = [];

		foreach ( $snippets as $snippet ) {
			$data[] = [
				'id'     => $snippet->id,
				'name'   => $snippet->name,
				'type'   => $snippet->type,
				'active' => $snippet->active,
			];
		}

		return new WP_REST_Response( $data, 200 );
	}

	/**
	 * Perform the necessary actions to add a button to the TinyMCE editor
	 */
	public function setup_mce_plugin() {
		if ( ! code_snippets()->current_user_can() ) {
			return;
		}

		/* Register the TinyMCE plugin */
		add_filter(
			'mce_external_plugins',
			function ( $plugins ) {
				$plugins['code_snippets'] = plugins_url( 'dist/mce.js', PLUGIN_FILE );
				return $plugins;
			}
		);

		/* Add the button to the editor toolbar */
		add_filter(
			'mce_buttons',
			function ( $buttons ) {
				$buttons[] = 'code_snippets';
				return $buttons;
			}
		);

		/* Add the translation strings to the TinyMCE editor */
		add_filter(
			'mce_external_languages',
			function ( $languages ) {
				$languages['code_snippets'] = __DIR__ . '/mce-strings.php';
				return $languages;
			}
		);
	}

	/**
	 * Enqueue the syntax highlighting assets if they are required for the current posts
	 *
	 * @param array<WP_Post|int>|null|false $posts List of currently visible posts.
	 *
	 * @return array<WP_Post|int>|null|false Unchanged list of posts.
	 */
	public function enqueue_highlighting( $posts ) {

		// Exit early if there are no posts to check or if the highlighter has been disabled.
		if ( empty( $posts ) || Settings\get_setting( 'general', 'disable_prism' ) ) {
			return $posts;
		}

		// Loop through the posts, checking for an existing shortcode, short-circuiting if possible.
		$found_shortcode_content = null;

		foreach ( $posts as $post ) {
			if ( false !== stripos( $post->post_content, '[' . self::SOURCE_SHORTCODE ) ||
			     false !== strpos( $post->post_content, '<!-- wp:code-snippets/source ' ) ) {
				$found_shortcode_content = $post->post_content;
				break;
			}
		}

		// Load assets on the appropriate hook if a matching shortcode was found.
		if ( null !== $found_shortcode_content ) {
			$this->register_prism_assets();

			add_action(
				'wp_enqueue_scripts',
				function () {
					wp_enqueue_style( self::PRISM_HANDLE );
					wp_enqueue_script( self::PRISM_HANDLE );
				},
				100
			);
		}

		return $posts;
	}

	/**
	 * Enqueue the styles and scripts for the Prism syntax highlighter.
	 *
	 * @return void
	 */
	public static function register_prism_assets() {
		$plugin = code_snippets();

		wp_register_style(
			self::PRISM_HANDLE,
			plugins_url( 'dist/prism.css', $plugin->file ),
			array(),
			$plugin->version
		);

		wp_register_script(
			self::PRISM_HANDLE,
			plugins_url( 'dist/prism.js', $plugin->file ),
			array(),
			$plugin->version,
			true
		);
	}

	/**
	 * Enqueue all available Prism themes.
	 *
	 * @return void
	 */
	public static function enqueue_all_prism_themes() {
		self::register_prism_assets();

		wp_enqueue_style( self::PRISM_HANDLE );
		wp_enqueue_script( self::PRISM_HANDLE );
	}

	/**
	 * Print a message to the user if the snippet ID attribute is invalid.
	 *
	 * @param integer $id Snippet ID.
	 *
	 * @return string Warning message.
	 */
	protected function invalid_id_warning( int $id ): string {
		// translators: %d: snippet ID.
		$text = esc_html__( 'Could not load snippet with an invalid ID: %d.', 'code-snippets' );
		return current_user_can( 'edit_posts' ) ? sprintf( $text, $id ) : '';
	}

	/**
	 * Allow boolean attributes to be provided without a value, similar to how React works.
	 *
	 * @param array<string|number, mixed> $atts          Unfiltered shortcode attributes.
	 * @param array<string>               $boolean_flags List of attribute names with boolean values.
	 *
	 * @return array<string|number, mixed> Shortcode attributes with flags converted to attributes.
	 */
	protected function convert_boolean_attribute_flags( array $atts, array $boolean_flags ): array {
		foreach ( $atts as $key => $value ) {
			if ( in_array( $value, $boolean_flags, true ) && ! isset( $atts[ $value ] ) ) {
				$atts[ $value ] = true;
				unset( $atts[ $key ] );
			}
		}

		return $atts;
	}

	/**
	 * Evaluate the code from a content shortcode.
	 *
	 * @param Snippet              $snippet Snippet.
	 * @param array<string, mixed> $atts    Shortcode attributes.
	 *
	 * @return string Evaluated shortcode content.
	 */
	protected function evaluate_shortcode_content( Snippet $snippet, array $atts ): string {	
		if ( empty( $atts['php'] ) ) {
			return $snippet->code;
		}

		/**
		 * Avoiding extract is typically recommended, however in this situation we want to make it easy for snippet
		 * authors to use custom attributes.
		 *
		 * @phpcs:disable WordPress.PHP.DontExtract.extract_extract
		 */
		extract( $atts );

		ob_start();
		eval( "?>\n\n" . $snippet->code . "\n\n<?php" );

		return ob_get_clean();
	}

	/**
	 * Render the value of a content shortcode
	 *
	 * @param array<string, mixed> $atts Shortcode attributes.
	 *
	 * @return string Shortcode content.
	 */
	public function render_content_shortcode( array $atts ): string {
		$atts = $this->convert_boolean_attribute_flags( $atts, [ 'network', 'php', 'format', 'shortcodes', 'debug' ] );
		$original_atts = $atts;

		$atts = shortcode_atts(
			[
				'id'         => 0,
				'snippet_id' => 0,
				'network'    => false,
				'php'        => false,
				'format'     => false,
				'shortcodes' => false,
				'debug'      => false,
			],
			$atts,
			self::CONTENT_SHORTCODE
		);

		$id = 0 !== intval( $atts['snippet_id'] ) ? intval( $atts['snippet_id'] ) : intval( $atts['id'] );
		if ( ! $id ) {
			return $this->invalid_id_warning( $id );
		}

		$snippet = get_snippet( $id, (bool) $atts['network'] );

		// Render the source code if this is not a shortcode snippet.
		if ( 'content' !== $snippet->scope ) {
			return $snippet->id ? $this->render_snippet_source( $snippet ) : $this->invalid_id_warning( $snippet->id );
		}

		// If the snippet is inactive, either display a message or render nothing.
		if ( ! $snippet->active ) {
			if ( ! $atts['debug'] ) {
				return '';
			}

			/* translators: 1: snippet name, 2: snippet edit link */
			$text = __( '<strong>%1$s</strong> is currently inactive. You can <a href="%2$s">edit this snippet</a> to activate it and make it visible. This message will not appear in the published post.', 'code-snippets' );

			$edit_url = add_query_arg( 'id', $snippet->id, code_snippets()->get_menu_url( 'edit' ) );
			return wp_kses(
				sprintf( $text, $snippet->name, $edit_url ),
				[
					'strong' => [],
					'a'      => [
						'href' => [],
					],
				]
			);
		}

		$content = $this->evaluate_shortcode_content( $snippet, $original_atts );

		if ( $atts['format'] ) {
			$functions = [ 'wptexturize', 'convert_smilies', 'convert_chars', 'wpautop', 'capital_P_dangit' ];
			foreach ( $functions as $function ) {
				$content = call_user_func( $function, $content );
			}
		}

		if ( $atts['shortcodes'] ) {
			// Remove this shortcode from the list to prevent recursion.
			remove_shortcode( self::CONTENT_SHORTCODE );

			// Recursion depth is limited to prevent infinite loops.
			static $depth = 0;
			$max_depth = self::MAX_SHORTCODE_DEPTH;

			// Find the shortcode in the content and replace it with the evaluated content.
			$content = preg_replace_callback(
				'/\[' . self::CONTENT_SHORTCODE . '([^\]]*)\]/',
				function ($matches) use (&$depth, $max_depth) {
					if ($depth >= $max_depth) {
						return '<!-- Max shortcode depth reached -->';
					}
					$depth++;
					$atts = shortcode_parse_atts($matches[1]);
					$result = $this->render_content_shortcode($atts);
					$depth--;
					return $result;
				},
				$content
			);

			// Add this shortcode back to the list.
			add_shortcode( self::CONTENT_SHORTCODE, [ $this, 'render_content_shortcode' ] );
		}

		return apply_filters( 'code_snippets/content_shortcode', $content, $snippet, $atts, $original_atts );
	}

	/**
	 * Converts a value and key into an HTML attribute pair.
	 *
	 * @param string $value Attribute value.
	 * @param string $key   Attribute name.
	 *
	 * @return void
	 */
	private static function create_attribute_pair( string &$value, string $key ) {
		$value = sprintf( '%s="%s"', sanitize_key( $key ), esc_attr( $value ) );
	}

	/**
	 * Render the source code of a given snippet
	 *
	 * @param Snippet              $snippet Snippet object.
	 * @param array<string, mixed> $atts    Shortcode attributes.
	 *
	 * @return string Shortcode content.
	 */
	private function render_snippet_source( Snippet $snippet, array $atts = [] ): string {
		$atts = array_merge(
			array(
				'line_numbers'    => false,
				'highlight_lines' => '',
			),
			$atts
		);

		$language = 'css' === $snippet->type ? 'css' : ( 'js' === $snippet->type ? 'js' : 'php' );

		$pre_attributes = array(
			'id'    => "code-snippet-source-$snippet->id",
			'class' => 'code-snippet-source',
		);

		$code_attributes = array(
			'class' => "language-$language",
		);

		if ( $atts['line_numbers'] ) {
			$code_attributes['class'] .= ' line-numbers';
			$pre_attributes['class'] .= ' linkable-line-numbers';
		}

		if ( $atts['highlight_lines'] ) {
			$pre_attributes['data-line'] = $atts['highlight_lines'];
		}

		$pre_attributes = apply_filters( 'code_snippets/prism_pre_attributes', $pre_attributes, $snippet, $atts );
		$code_attributes = apply_filters( 'code_snippets/prism_code_attributes', $code_attributes, $snippet, $atts );

		array_walk( $code_attributes, array( $this, 'create_attribute_pair' ) );
		array_walk( $pre_attributes, array( $this, 'create_attribute_pair' ) );

		$code = 'php' === $snippet->type ? "<?php\n\n$snippet->code" : $snippet->code;

		$output = sprintf(
			'<pre %s><code %s>%s</code></pre>',
			implode( ' ', $pre_attributes ),
			implode( ' ', $code_attributes ),
			esc_html( $code )
		);

		return apply_filters( 'code_snippets/render_source_shortcode', $output, $snippet, $atts );
	}

	/**
	 * Render the value of a source shortcode
	 *
	 * @param array<string, mixed> $atts Shortcode attributes.
	 *
	 * @return string Shortcode content.
	 */
	public function render_source_shortcode( array $atts ): string {
		$atts = $this->convert_boolean_attribute_flags( $atts, [ 'network', 'line_numbers' ] );

		$atts = shortcode_atts(
			array(
				'id'              => 0,
				'snippet_id'      => 0,
				'network'         => false,
				'line_numbers'    => false,
				'highlight_lines' => '',
			),
			$atts,
			self::SOURCE_SHORTCODE
		);

		$id = 0 !== intval( $atts['snippet_id'] ) ? intval( $atts['snippet_id'] ) : intval( $atts['id'] );
		if ( ! $id ) {
			return $this->invalid_id_warning( $id );
		}

		$snippet = get_snippet( $id, (bool) $atts['network'] );

		return $this->render_snippet_source( $snippet, $atts );
	}
}